This application claims priority from Japanese patent application No. 2000-84944, filed on Mar. 24, 2000, the complete disclosure of which is hereby incorporated herein by reference.
1. Field of the Invention
This invention is related to a glittering paint and a glittering coated film. The glittering paint for obtaining a glittering coated film according to the present invention comprises a coated film forming polymer, a glittering pigment and a solvent. Use of the glittering pigment results in a glittering surface, for example, of metallic tone.
The glittering paint according to this invention is suitable for formation of a glittering coated film on plastic exterior articles of an automobile such as front grills, usually based on ABS resin material, and wheel caps, usually made of PP (polypropylene) substrate, requiring high glitter appearance.
The present invention discloses an exemplary method for forming a glittering surface of metallic tone as the glittering surface, however the present invention is applicable also for the formation of other aesthetic glittering surfaces, such as, for example, of ceramic tone (tone of pottery or china).
The abbreviations used in the present specification are as follows. xe2x80x9cNVxe2x80x9d is an abbreviation for xe2x80x9cnon volatilexe2x80x9d and NV % means a non-volatile content (paint solid content) concentration. xe2x80x9cPWCxe2x80x9d is an abbreviation for xe2x80x9cpigment weight concentrationxe2x80x9d, denoting the content of the pigment in the coated film(coated film ingredient). xe2x80x9cMwxe2x80x9d is an abbreviation for the xe2x80x9cweight average molecular weightxe2x80x9d, converted as polystyrene.
2. Description of Related Art
It is well known that glittering surfaces of metallic tone can be obtained conventionally by either applying metal foils or depositing metal membranes by vapor deposition to substrates or the like. However, it is difficult to uniformly apply the metal foils on substrates of a complicated shape having uneven surfaces, because of the locally occurring creasing problem. Furthermore, a special vacuum apparatus is required for the vapor deposition in the method of depositing metal membranes, which makes it difficult to apply the method to large size substrates.
In view of the above shortcomings, a method for forming a glittering coated film having a glittering surface of metallic tone, with a structure as shown in FIG. 1., has been proposed in Japanese Laid-Open Patent No. 80620/1999.
A base coated film (primary layer), 14 is formed on a substrate (plastic molding product), 12, a metallic paint is coated on the base coated film, 14 to form a metallic tone layer (glittering layer) 16, and then a top coat layer (clear coated film) 18 is formed.
Preferred metallic paints disclosed in the Japanese Patent are those containing metal flakes (metal powder with high aspect ratio) which are prepared by pulverizing vapor deposited metal films of glittering pigment, 20. In order to achieve glittering appearance of the base coated film, 14, it is necessary to orient the glittering pigment, 20 in a planar arrangement. Therefore, it is desirable that the glittering layer (metal tone layer), 16 be as thin as possible (2 xcexcm or less).
In order to achieve the desired looks of high glitter, it is necessary to form the thin metallic tone layer 16 by applying a metallic paint of high PWC (15% or more) onto the baked base coated film 14, followed by formation of the top coat layer (clear coated film) for protection. All of the metallic paints used in the illustrative examples of the Japanese Patent have PWC: 100%, except for Preparation Examples 4, 5 as shown in Table 1. The results show in Table 2, examples 4, 5, 10 and 11 demonstrate that in the Preparation Examples 4, 5 with PWC of 20% and 10%, sufficient gloss (glittering property) cannot be easily obtained if the baking temperature of the base layer is low.
Therefore, in the method of forming the glittering coated film as described in the Japanese Laid-Open Patent No. 80620/1999, it is necessary not only to use a relatively high amount of pulverization product of vapor deposited films as the glittering pigment, but also to use a primer layer to level the surface of the substrate, and to sufficiently heat the primer layer to cure the primer layer.
The object of this invention is to provide a glittering paint and a glittering coated film which does not necessarily require formation of a primer layer and/or clear top coat layer.
Another object of this invention is to provide a glittering paint capable of producing a glittering coated film of metallic tone, without using a great amount of pulverization products of vapor deposition films.
A glittering paint for producing or obtaining a glittering coated film according to the present invention comprises:
a coated film forming polymer, a glittering pigment comprising an inorganic powder and a solvent,
wherein the coated film forming polymer comprises a pigment carrying polymer,
wherein the pigment carrying polymer has a weight average molecular weight (Mw) of at least 50,000 and a refractive index (by Abbe""s refractometer) (nD) of at least 1.48,
the coated film forming polymer has an overall weight average molecular weight (Mw) of at least 50,000,
the inorganic powder has an aspect ratio (the ratio of the length or diameter of a particle to the thickness of the particle) of at least 50 and,
the glittering pigment weight concentration (PWC) in the coated film is 15% or less.
In the glittering paint described above, excellent appearance of glittering can be easily obtained by using glittering pigment comprising a inorganic powder having an aspect ratio of 250 to 500 (mainly metal powder).
The metal powder with the aspect ratio within the range described above can be obtained easily by pulverizing vapor deposition films of aluminum or the like.
The pigment carrying polymer may be selected from one or more of cellulose polymers or one or more of polar group containing vinyl polymers, preferably, one or more of polar group introduced polyolefins.
A glittering coated film comprising at least one layer and having a glittering surface according to the present invention can be formed by applying the glittering paint as described above to a substrate and forming a glittering layer to a thickness of 5 to 20 xcexcm on the substrate.
Performance of the coated article can be significantly improved when a clear coat film layer is applied on the glittering layer forming coated glittering film.